1. Field of the Invention
This invention relates to ultrasonic devices for cosmetic and dermatological applications. More particularly, the invention is concerned with methods and apparatus facilitating the use of ultrasonic energy coupled to anatomical tissue to precondition the skin to allow the penetration of medical and cosmetic compounds, to drive these compounds into and through the epidermis, into the dermis, into the anatomical tissue below the dermis and into the blood supply when required. The invention is particularly effective to control the depth of penetration and the dosage of medications to be delivered to eliminate the harmful side effects associated with some of the systemically delivered medications.
2. Description of Prior Art
Numerous attempts have been made in the past to deliver medications through the skin by chemical, electrical and ultrasonic means. The application of chemicals to modify the skin structure to allow the penetration of drugs was found to be dangerous because while it provided access for drugs to penetrate, it left the body unprotected against harmful environments. The application of electrical fields to create transient transport pathways by a method called electroporation, and the method to electrically charge drug molecules to increase their penetration through the skin called iontophoresis, have both been proven ineffective to deliver therapeutically adequate dosage of medications through the skin. Past applications of high frequency (0.5 to 3 megahertz) and high intensity (0.5 to 5 W/cm.sup.2) therapeutic ultrasound, called sonophoresis, were found to be uncertain, inefficient, and the method found limited clinical applications.
The efforts of the prior art of ultrasonically induced drug delivery (sonophoresis) were focused on driving drug molecules through the skin by the applications of high (megahertz) frequency high energy ultrasonic pressure waves. This procedure particularly suffered from the disadvantage of tissue heating and the associated modification and sometimes destruction of healthy cells. Once adequate ultrasonic power is applied either in a continuous wave ultrasonic modality, or maximum burst length that is practicable without adverse tissue heating effects to force drug molecules through the highly resistive outermost sealing layer of the skin, the stratum corneum (SC), the drugs typically will proceed uncontrollably through the less resistive dermis into the blood system, creating systemic absorption of the drugs which is undesirable in most dermatological applications.
What has occurred to date is that notwithstanding the teachings of the prior art, the ability to deliver dermatological drugs topically, safely, effectively, inexpensively, and easily in a home environment has remained unsolved.
Responding to the above described unresolved needs, the object of this invention is to provide a method and apparatus for the pretreatment of the skin to open up passageways through the epidermis and to allow the penetration of medications or cosmetics for a limited time period, in such a method which seals the skin automatically within a short period of time after the topical application of the drugs to restore the environmental protection of the body.
Another object of the invention is to provide a method and apparatus of ultrasound medicated drug delivery where the amount of the drug (dosage) and the depth of the penetration of the drug is controlled.
A further object of the invention is the elimination of paring of warts to provide access for the therapeutic compounds into the deeper structure of the warts, without surgical procedures. This is a particularly important feature when treating AIDS patients.
Yet another object of the invention is to provide a method and apparatus to speedily restore the sealing properties of the skin upon the completion of the ultrasound medicated delivery of the medication and to provide immediate environmental protection of the body. Further objects and advantages will be apparent from the examination of the drawings and the specification.